Currently, the detection and imaging of tagged molecules in small animals, requires that the animal be rendered unconscious through the inhalation or injection of anesthetics or alternatively, physically restrained. These procedures are inherently undesirable because of the likelihood that the anesthesia or restraint will introduce complicating factors to the biological phenomenon under study. This is particularly an issue in neurological and brain function studies that are being done with small animals such as rats and mice. In addition, there is a substantial risk that the animal will be killed by the procedure, which event can carry a high cost in time resources and the overall effort, especially when the animal under study has been specially bred. Also, if several studies are planned for the same animal, it is not possible to subject the animal to too many episodes of anesthesia in a given period of time. In such studies, it is often desirable to follow the functional, metabolic or molecular activity for extended periods of time, extending through phases of animal activity such as sleep, active, etc. depending upon the type of label used to monitor a particular function (for example, uptake, washout times, isotope half life, etc.).
There therefore exists a need for a method and apparatus to perform such studies that does not require the anesthetization or other immobilization of such animals during the performance of such studies with all of the attendant risks to the animal.